How did you choose your lover? Sexual selection is more than a choice of position, though that is by far the most fun definition.

"Tonight's sexual selection shall be....the reverse cowgirl."

In evolutionary psychology, sexual selection refers to the idea that specific traits evolved over time for the purpose of attracting a mate, and not for survival. Examples in the animal kingdom would include the dancing ability of a bird, or bright colors on a frog.

In couples therapy sessions, trust is a major player in both initial attraction and staying together, so much so that it is an evolutionarily selected for trait. It seems that trust issues are among the most distressing for all parties, particularly across the genders.

Man: "I didn't do the dishes like I said I would. BFD."Woman: "He didn't do the dishes. I can't trust what he says. Maybe he's fucking my sister."

While I might be revving up the dramatics a bit, there is a tendency to be more sensitive to smaller cues in times of relationship distress, and with good reason. Both sexes evolved to be so sneaky in our sexual strategies that we developed equally sensitive internal lie detectors. That may be the portion of our psyche we listen to most carefully in choosing our mates and in deciding to stay together through stressful times.

The uterus may be the most sneaky of all.

Cryptic Ovulation: Sneaky, Sneaky Uterus

Cryptic ovulation refers to the idea that women ovulate secretly, and it may have evolved in direct relation to how sneaky the men around us were. If we found ourselves in an environment where mating strategies were less altruistic and more inclined towards lying and cheating mates or where violence towards the offspring of others was the norm, we needed a good way to confuse paternity and increase odds for survival. While a woman--if she knows what to look for--can identify when she is ovulating, it is nearly impossible for others to tell. This means that ensuring a child's paternity is far more difficult for men.

Just ask Maury Povich.

There are several theories as to why hidden ovulation developed, as discussed by Robert Wright in his book The Moral Animal1. One holds that through hidden ovulation, women were able to secure provisioning for longer periods of time than they would have been able to otherwise.

Another contends that by allowing several men to think they may have fathered a child, it encouraged each to provide a little to that offspring, or at least make them less likely to harm the kid.

"I swear, he's yours. He just takes after my side of the family. My grandmother was 1/8 Greek on her father's side..."

Another holds that if a women wished to have a child with the best possible genes, but needed more resources then an attractive man could provide, the most appropriate strategy would have been to mate with the genetically superior specimen during ovulation, then trick a more resourceful male into providing financially.

"I got a husband with a pool house, now all I need is a pool boy..."

Our flexible breeding patterns suggest that all may have some merit, so it is easy to see how trust became paramount. Hidden ovulation in the human species required that a male needed to trust his partner so as not to provision another man's child, at least in cultures where children were not reared cooperatively.

Faithfulness of men was important to women too, but for different reasons. According to evolutionary psychologist David Buss, in his book The Evolution of Desire, women's sexual strategy revolved around securing provisioning and protection2. If a man was not faithful and sired children with another female, he would have less resources for her children.

Women, Buss says, are more discerning based on the higher burden of pregnancy and childrearing, and the fact that they only have so many opportunities to mate. (Keep in mind that mate refers to having children and not to sex itself, because we are not as discerning in casual sex.) For mating, women also look for positive genetics, like humor and smarts. Brains over shots, fellas.

Women also seek emotional stability, and all the trust cues that come with that. She may look for things like kindness towards children, and assistance in caregiving, which may serve as a sign that she can trust her partner to help her care for their offspring. According to Buss, provisioning females financially, while it appears shallow--and makes the feminist in me wince--is also a cue that he will provide support for her and their children in the long run (financial or provisional trust).

Evolutionary psychologists say: "If you like it, put a ring on it."

But really, she wants way more than a ring. She wants honesty. She probably wants fidelity. She wants to know you appreciate all the awesomeness that is her. And, maybe most of all, she wants help with the fucking dishes every once in awhile.